Rheostat



G. H. WHITTINGHAM Oct. 9, 1928.

RHEOSTAT I filed March 23, 1925 2- Sheets-Shet 1 {db 5] maamto'a attorney Oct. 9, 1928.

G. H. WHITTINGHAM RHEOSTAT Filed March 23. 1925 2 Sheets-Sheet 2 "IIIIIIIIIIIIIZ I Skye/141501- Patented Oct. 9, 1928..

UNITED STATES testes? eaten-r or'rica.

GEORGE E. WHI'ETINGHAM, OF BALTIMORE, MARYLAND, ASSIGNOR T0 MQNI'EOR- GON- raornnn commas, or nanrnronn, mun.

MARYLIsND, A CORYORATION 01E MARY- Application filed March 23, 1925. Serial No. 17,628.

This invention relates to improvements in the type of rheostat illustrated in my copending' application Serial No. 7 25,555, filed July 12, 1924, .in which edgewound resistance coils are mounted upon supporting members each composed of a metal bar having a covering of refractory insulating material provided with threads for receiving the coil, the covering for the bar being composed of relatively short sections arranged end to end and interlocking with the bar. The present invention embodies improvements in themanner'of mounting the sections of insulating mate-r al upon'the bars which carry the coils; also to details of the rheostat frame and the means for mounting the coil supporting bars porting" bars;

Fig. 6 is a section on the line 6-6 of Fig. l, showing, in detail the manner in which the coil supporting bars are mounted on the cross bars of the frame; and,

Fig". 7 is a perspective view showing the elements composing the frame of the rheostat.

In the accompanyingdrawing, a and a in-.

dic'ate two similar frames, one supported upon the other, and each frame supporting a plurality of resistance units, indicated at r in the frame a, and at r in the frame a. Each resistance unit comprises a flat metal supporting bar 6, shown in side view in Figs. 2 and 4:, an insulating; covering 0 of refractory material, and a resistance coil a, threaded on to said covering. Each supporting bar I) has a forked end 1 and a hooked end 2. The bar also has shoulders 3 and 4, at its opposite edges adjacent the forkedend 1, and it has similar shoulders 5 and 6 adjacent the end 2. The shoulder 3 is offset from the shoulder 4, and

the shoulder 5 is offset from the shoulder 6,-

and the distance between the shoulders 3 and 5 is the same as the distance between the shoulof insulating; material fit over the edges of the bar, and in placing these sections upon the bar, two sections, such as 7 and 7", in Fig. 2, are placed against the shoulders 3 and 4, respectively, and the other sections 8, 9, etc. on one edge of the bar are arranged end to end, and the sections 8, 9, are arranged end to end on the. opposite edge of the bar so that two series of opposing sections are built up upon the bar to any desired length. The shoulders? and t are off-set from one another longitudinally of the bar one-half the distance between the. centers of adjacent teeth on one of the porcelain sections, so that when the covering is on the bar, the threads on the sections 7, 8, 9, etc, will be olfset from the threads 7*, 8, 9*" etc. the proper distance to receive the convolutions of the helix d. It will be seen that by providing the offset shoulders on the bar and by placing the end sec" tions of the insulating material against these shoulders, the threads on all of the sections will be properly placed to receive the helix. To facilitate applying; the sections of insulatin material to the supporting bar, I prefer ab y apply to the opposite sides of the bar thin layers 10 of asbestos, which are secured by suitable cement, and when the porcelain sections are applied to the bar, they are held thereon frictionally and adhesively by the asbestos and cement. The coils are composed of flat ribbons of metal wound on edge and these are readily applied by threading them on to the covering. This may be accomplished by turning either the coil or the bar in a lathe,

Each of the frames (1, a, for supporting the assembled resistance units, is composed of two flat side bars 11, connected at their ends by bolts or end bars 12, and these bolts pass centrally through flat frame supporting bars 13, which extend at right angles to the side bars and have their ends 13 turned over at right angles to their body portions and in the same direction. The end bars or bolts lain pa 12, as shown in Fig. 6, are covered by tube 14 of insulating material, preferably mica. The forked ends 1 ofthe coil supporting bars fit over the insulating tubing on one of the bolts 12, and the l'lOOlK'EBCl ends 2 of the'side bars rest upon the insulating tubing upon the other bolt 12. Washers 15 of insulating material are placed on each side of the ends of the bars 6, and these bars are spaced apart by sections of metal tubinglli and by metal washers 1'? which are arranged between the ends of the spacing tubes and the insulating Washers 15. The bolts 12 are provided with nuts 18 at their ends, and by tightening these nuts the spacing tubes will be forced together and the coil supporting bars will be firmly held in position. it he tightening of these nuts also tightens the members of the frames.

The side bars of the frames are alike in form and each has overturned ends 11 Which bear against edges of the trame supporting members l3 and hold these in their upright positions before the nuts 18 are tightened. The members 13 also are all alike. It Will be seen that the supporting frames are composed of few parts, and that a frame to suit any desired number of coils can be quickly assembled by selecting end bolts ot a len th to suit the number of coils and bolt ing the parts together.

the overturned ends 13 on the supports 13 serve as a means for connecting a plurality of trames together. Thus, as shown in 3, the a a" are secured together by bolts passing through the adjacent overturned ends at the members 13 on both frames. As many frames as desired may be thus secured together. in connecting a num her of frames together, the nuts 18 on the end bolts or bars are not firmly tightened until. the trainee are assembled. After the memhers in the several frames have been properly lined up and bolted together, the nuts on the end bolts may be tightened and the Whole structure will then be a rigid frame composed of several similar frames.

lln the drawing, it have shown terminal clamps P 29' on some or the coils and connectors t between adjacent coils, but these features need not be described herein as they are not a part of the present invention but are claimed in my co pending application referi d to above,

ls l have shown a pair of offset shoulders or stops, 3- t, at one end of each coilsupporting bar, and a similar pair 5-6 at the opposite end, -so that the operation of assembling the porcelain parts may be commenced it either end of the bar, it will be obvious that only one of shoulders is essential -for correctly posi ioning norco res on the bar, that other pair may be omitted.

Wha It claim is:

l. in a 'rheostat, a metal bar having 2. in a rheostat, a metal bar having a rela-' tively fiat threaded insulating covering thereon adapted to receive a helix of resistance metal, said covering comprising two opposing series of lilre sections having threads on their outer edges and said bar having stops oit'set from one another longitudinally of the bar for positioning the end section of one series a definite distance in advance of the corresponding section of the opposing series.

3'. in a rheostat, a flat metal bar having shoulders on its opposite edges, near one end, and o'fiset from one another longitudinally of the bar, an insulating covering for the bar comprising two opposing series of like sec tions, each section channeled to lit the bar and having threads on its outer edge, and the end section of each series fitting against one of said shoulders.

l. in a rheostat, a pair of similar fiat metal strips, constituting side bars, frame-supporting members comprising similar lat metal strips arranged at right angles to the side bars, said members having their ends turned at right angles'to their central portions, bolts extending through the central parts of said members and through the end portions of the side bars, spacing members on the bolts, coil supporting bars having their ends supported by the bolts between the spacing members and insulated from the bolts, and means on the ends of the bolts for clamping the various parts on the bolts together.

5. In a rheostat, a pair of similar fiat metal strips, constituting side bars, each strip having flanges at its ends, trame-supportiug members comprising similar flat metal strips arranged at right angles to the side bars and. against said flanges, said members having their ends turned at right angles to their central portions, bolts extending through the central parts of said members and through the end portions of the side bars, spacing members on the bolts, coil-supporting bars having their ends supported by the bolts be tween the spacing members and insulated from the bolts, and means on the ends of the bolts tor clamping the various parts on the bolts together.

in testimony whereof l hereunto ailix my signature.

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